The wafers that serve as the substrates for semiconductor elements are sliced from elongated crystals (billets) of material, typically silicon, germanium, or gallium arsenide. The wafers are obtained by sawing the crystals into very thin slices (about a half millimeter thick). These slices are then lapped and polished.
Residual film from lubricants used during slicing as well as air-borne particulates and particles of semiconductor material removed by lapping and polishing tend to adhere to the surfaces of the wafers. This detritus must be removed prior to further processing of the wafers (e.g., masking and etching) to maintain the ultraclean conditions required for such further processing.
Accordingly, in the field of semiconductor manufacture, considerable attention has been directed toward providing devices that are capable of thoroughly cleaning both surfaces of a semiconductor wafer.